Pen Type Drug Injection Device with Absolute Angular Dose Encoder Mechanism

ABSTRACT

A drug delivery device comprising: a housing; a cylindrical member rotatably supported within the housing; and a plurality of sensors; wherein: the outer surface of the cylindrical member is provided with a single track, the track forming an encoder and having a plurality of first track segments and a plurality of second track segments arranged along the length of the track which are respectively capable of inducing first and second responses in the sensors; and in each rotational position of the cylindrical member relative to the housing at least one different first track segment is capable of inducing a first response in at least one said sensor, thereby enabling the rotational position of the cylindrical member relative to the housing to be determined.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. National Phase application pursuant to35 U.S.C. §371 of International Application No. PCT/EP2014/050470 filedJan. 13, 2014, which claims priority to European Patent Application No.13151374.9 filed Jan. 15, 2013. The entire disclosure contents of theseapplications are herewith incorporated by reference into the presentapplication.

FIELD OF INVENTION

The present invention relates to a drug delivery device.

BACKGROUND

Pen type drug delivery devices have application where regular injectionby persons without formal medical training occurs. This is increasinglycommon among patients having diabetes where self-treatment enables suchpatients to conduct effective management of their diabetes.

For good or perfect glycemic control, the dose of insulin or insulinglargine has to be adjusted for each individual in accordance with ablood glucose level to be achieved. The present invention relates toinjectors, for example hand-held injectors, especially pen-typeinjectors, that is to injectors of the kind that provide foradministration by injection of medicinal products from a multidosecartridge. In particular, the present invention relates to suchinjectors where a user may set the dose.

A user undertaking self-administration of insulin will commonly need toadminister between 1 and 80 International Units.

SUMMARY

According to an aspect of the invention there is provided a drugdelivery device comprising: a housing; a cylindrical member rotatablysupported within the housing; and a plurality of sensors; wherein: theouter surface of the cylindrical member is provided with a single track,the track forming an encoder and having a plurality of first tracksegments and a plurality of second track segments arranged along thelength of the track which are respectively capable of inducing first andsecond responses in the sensors; and in each rotational position of thecylindrical member relative to the housing at least one different firsttrack segment is capable of inducing a first response in at least onesaid sensor, thereby enabling the rotational position of the cylindricalmember relative to the housing to be determined.

Advantageously, this enables the absolute rotational position of thecylindrical member relative to the housing to be determined using asingle track.

The cylindrical member may be supported within the housing andconfigured to be rotated relative to the housing and the sensors.

The cylindrical member may be movable along a helical path between aplurality of discrete positions. Preferably, each discrete position isbeing associated with a specific dose amount.

In each discrete position of the cylindrical member the sensors arerespectively capable of having induced therein a first or secondresponse by one said first or second track segment.

In each of the discrete positions of the cylindrical member a uniquecombination of first and second responses is capable of being inducedacross the plurality of sensors.

Each discrete position of the sensors along the track may be associatedwith a unique binary code.

The plurality of sensors may be arranged along a single track. Theplurality of sensors may be configured to enable interaction with uniqueconfigurations of first and second track segments. Preferably, theplurality of sensors interacts with unique configurations of first andsecond track segments whenever an increment of insulin is dialed ordispensed.

The device may further comprise a processor configured to determine therotational position of the cylindrical member relative to the housing byanalysing signals output from each of the sensors which correspond withwhether a first said response or a second said response is induced in arespective said sensor.

The sensors may each comprise an electrical contact, and the first andsecond track segments may respectively have lower and higher values ofelectrical resistance, the first track segments being electricallycoupled to one another.

The processor may be configured to cause an electrical signal to beapplied to one of the electrical contacts while simultaneously detectingwhether any of the other electrical contacts are energised, therebyenabling the rotational position of the cylindrical member relative tothe housing to be determined.

The processor may be configured to cause an electrical signal to beapplied to each of the first track segments via an additional electricalcontact while simultaneously detecting whether any of the otherelectrical contacts are energised, thereby enabling the rotationalposition of the cylindrical member relative to the housing to bedetermined.

Advantageously, this enables the absolute rotational position of thecylindrical member relative to the housing to be directly determined byanalysing which of the electrical contacts are energised.

The additional electrical contact may engage a section of the trackwhich electrically couples the first track segments to one another.

The device may further comprise an additional track located adjacent thetrack forming said encoder, said additional track being electricallyconductive and in engagement with a further electrical contact, whereinthe processor may be configured to analyse signals from the furtherelectrical contact to determine the operational mode of said device.

Advantageously, this enables whether the device is in dialing mode ordrug dispensing mode to be determined.

The device may further comprise a switch configured to electricallycouple the two tracks in one operational mode of said device, and toelectrically decouple the two tracks in another operational mode of saiddevice.

The device may further comprise a delivery button configured to causeexpulsion of a drug from the drug delivery device upon actuation thereofby a user, wherein depression of the delivery button changes a state ofthe switch.

The sensors may each comprise an optical sensor, and the first andsecond track segments may respectively comprise differently colouredparts of said track.

The processor may be configured to determine which of said opticalsensors are directed towards a first track segment and which of saidoptical sensors are directed towards a second track segment, therebyenabling the rotational position of the cylindrical member relative tothe housing to be determined.

Advantageously, this enables the absolute rotational position of thecylindrical member relative to the housing to be directly determined byanalysing which types of track segment the optical sensors are directedtowards.

The device may further comprise a sleeve which surrounds at least partof said cylindrical member and which rotates relative to the opticalsensors in one operational mode of the device but not in anotheroperational mode of the device, and an additional optical sensor for usein monitoring the rotational position of opaque markings provided on thesleeve in order to determine the mode of operation of the device.

Advantageously, this enables whether the device is in dialing mode ordrug dispensing mode to be determined.

The processor may be configured to determine a selected drug dose bysearching a lookup table stored in a memory, the lookup table providinga conversion between a rotational position of the cylindrical memberrelative to the housing and a selected drug dose.

The processor may be configured to determine a delivered drug dose bysubtracting a remaining drug dose from the selected drug dose.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 shows an external view of a drug delivery device 100 suitable forimplementing the present invention;

FIG. 2 shows a schematic diagram of some of the electronic componentspresent in the drug delivery device 100 of FIG. 1;

FIG. 3 shows a dose setting mechanism 400 of a drug delivery device 100suitable for use with the invention;

FIG. 4 shows detail of the dose setting mechanism 400 of FIG. 3;

FIG. 5 shows a close up of the region marked ‘A’ in FIG. 3;

FIG. 6 is an exploded view showing details of a driver forming part ofthe dose setting mechanism 400 of FIGS. 3 to 5;

FIG. 7 shows an encoded member 406 according to a first embodiment ofthe present invention;

FIG. 8 shows an external view of part of a drug delivery device 100according to a first embodiment of the present invention;

FIG. 9 shows a coded strip 300 suitable for use in manufacturing theencoded member 406 in FIG. 7;

FIG. 10 shows a graphical representation of the contacts 212 a-212 g inFIG. 8 (depicted as contacts 1 to 7) as they move over a coded strip300;

FIG. 11 shows a numerical representation of the coded strip 300 in FIG.9;

FIG. 12 shows an encoded member 406 according to a second embodiment ofthe present invention;

FIG. 13 shows an external view of part of a drug delivery device 100according to a second embodiment of the present invention;

FIGS. 14 a and 14 b respectively show front and rear views of an encodedmember 406 according to a third embodiment of the present invention;

FIG. 15 shows a coded strip 300 and an additional strip 308 suitable foruse in manufacturing the encoded member 406 in FIGS. 14 a and 14 b;

FIG. 16 shows an external view of part of a drug delivery device 100according to a third embodiment of the present invention;

FIG. 17 a shows an encoded member 406 which comprises part of a switch216;

FIG. 17 b shows a cross-sectional view of a switch 216 in a closedconfiguration;

FIG. 17 c shows the switch 216 in FIG. 17 b in an open configuration;

FIGS. 18 a and 18 b respectively show front and rear views of an encodedmember 406 according to a fourth embodiment of the present invention;

FIG. 19 shows an optically readable code suitable for use inmanufacturing an encoded member according to a fifth embodiment of thepresent invention;

FIG. 20 shows an encoded member 406 according to a sixth embodiment ofthe present invention;

FIG. 21 shows two opaque lines 446 surrounding a marking which definespart of the code located on the encoded member 406 in FIG. 20; and

FIG. 22 shows another encoded member provided with the code in FIG. 19.

DETAILED DESCRIPTION

Referring firstly to FIG. 1, an external view of a drug delivery device100 according to embodiments of the invention is shown. The device 100shown in FIG. 1 is a pen type injection device, having an elongatecylindrical shape, for setting and delivering a medicament, such asinsulin. The device 100 comprises a housing 102 having a first housingpart 104 and a second housing part 106. A rotatable dial 108 is locatedat a first (or proximal) end of the first housing part 104. Therotatable dial 108 has substantially the same outer diameter as thefirst housing part 104. The second housing part 106 may be detachablyconnected to the second end of the first housing part 104. The secondhousing part 106 is configured to have a needle (not shown) or similardrug delivery apparatus attached to it. To achieve this, the second (ordistal) end of the second housing part 106 may have a threaded portion110. The threaded portion 110 may have a smaller diameter than theremainder of the second housing part 106.

A display mount 112 is located on the first housing part 104. A displaymay be supported on the display mount 112. The display may be an LCDdisplay, a segmented display or any other suitable type of display. Thedisplay mount 112 may cover a recess (not shown) in the first housingportion 104. A number of electronic components, described in greaterdetail with reference to FIG. 2, may be disposed underneath the displaymount 112.

The first housing part 104 contains a drug dose setting and deliverymechanism. The second housing part 106 contains a drug cartridge (notshown). The drug contained in the drug cartridge may be a medicament ofany kind and may preferably be in a liquid form. The drug deliverymechanism of the first housing part 104 may be configured to engage withthe drug cartridge of the second housing part 106 to facilitateexpulsion of the drug. The second housing part 106 may be detached fromthe first housing part 104 in order to insert a drug cartridge or toremove a used cartridge. The first and second housing parts 104, 106 maybe connected together in any suitable way, for example with a screw orbayonet type connection. The first and second housing parts 104, 106 maybe non-reversibly connected together in such a way that the drugcartridge is permanently contained within the drug delivery device 100.Further the first and second housing parts 104, 106 may form part of asingle housing part.

The rotatable dial 108 is configured to be rotated by hand by a user ofthe drug delivery device 100 in order to set a drug dose to bedelivered. The dial 108 may be connected to an internal threading systemwhich causes the dial 108 to be displaced axially from the housing 102as it is rotated in a first direction. The dial 108 may be rotatable inboth directions or only in a first direction. The device 100 isconfigured, once a drug dose has been set by rotation of the rotatabledial 108, to deliver the set drug dose when a user exerts an axial forceat the proximal end of the device. The rotatable dial 108 may support adose delivery button (416 in FIG. 3) which must be depressed in order todeliver the set drug dose. The display 112 may be configured to displayinformation concerning the drug dose which has been set and/ordelivered. The display 112 may further show additional information, suchas the actual time, the time of the last usage/injection, a remainingbattery capacity, one or more warning signs indicating that a dialeddose has not been fully dispensed, and/or the like.

Referring now to FIG. 2, a schematic diagram of electrical circuitry 200forming part of the drug delivery device 100 is shown. The circuitry 200comprises a processor 202, a non-volatile memory such as a ROM 204, awritable non-volatile memory such as flash memory 205, a volatile memorysuch as a RAM 206, a display 210, contacts 212 (described later on ascontacts 212 a-212 i) and a bus 208 connecting each of these components.The circuitry 200 also comprises batteries 214 or some other suitablesource of power for providing power to each of the components and aswitch 216, described in greater detail below.

The circuitry 200 may be integral with the device 100. Alternatively,the circuitry 200 may be contained within an electronic module that canbe attached to the device 100. In addition, the circuitry 200 maycomprise additional sensors, such as optical or acoustical sensors. Thecircuitry 200 may comprise an audible alarm (not shown) which theprocessor 202 may control to sound an alarm when a dialed dose has notbeen fully dispensed.

The ROM 204 may be configured to store software and/or firmware. Thissoftware/firmware may control operations of the processor 202. Theprocessor 202 utilises RAM 206 to execute the software/firmware storedin the ROM to control operation of the display 210.

As such the processor 202 may also comprise a display driver. Theprocessor 202 utilises the flash memory 205 to store determined amountsof dose dialed and/or determined amounts of dose dispensed, as will bedescribed in more detail below.

The batteries 214 may provide power for each of the components includingthe contacts 212. The supply of electricity to the contacts 212 may becontrolled by the processor 202. The processor 202 may receive signalsfrom the contacts 212 and so could determine when the contacts areenergised, and is configured to interpret these signals. Information maybe provided on the display 210 at suitable times by operation of thesoftware/firmware and the processor 202. This information may includemeasurements determined from the signals received by the processor 202from the contacts 212.

A number of contacts 212 may be present in the device 100. For example,seven contacts 212 may be present and may be addressed individually bythe processor. In other embodiments, eight or nine contacts 212 arepresent. The contacts 212 may be mounted on an inner surface of thehousing 102.

A fuller explanation of the operation of the dose setting and deliverymechanism supported within the first housing part 104 will now be givenwith reference to FIGS. 3 to 6. FIG. 3 is a cross-sectional view of adose setting mechanism 400 of a drug delivery device 100. FIG. 4 is adetailed view of a portion of the dose setting mechanism 400. FIG. 5illustrates a close up view of the region marked ‘A’ in FIG. 3.

The dose setting mechanism 400 comprises an outer housing 404, an innerhousing 408 and an encoded member 406. These components are preferablyhollow cylinders arranged concentrically. The encoded member 406 isdisposed between the outer and inner housings 404, 408. The innerhousing 408 comprises a groove 432 provided along an external surface434 of the inner housing 408. A groove guide 436 provided on an innersurface 438 of the encoded member 406 is rotatably engaged with thisgroove 432. The encoded member 406 has information encoded on its outersurface 440 (see FIG. 7 for example) as will be described in more detailbelow.

A dose dial grip 402 is located at a proximal end of the outer housing404. The dose dial grip 402 is disposed about an outer surface of aproximal end of the encoded member 406. An outer diameter of the dosedial grip 402 preferably corresponds to the outer diameter of the outerhousing 404. The dose dial grip 402 is secured to the encoded member 406to prevent relative movement between these two components. The dose dialgrip 402 is represented in the external view of FIG. 1 by the rotatabledial 108. The dose dial grip 402 supports a dose delivery button dosedelivery button 416 which has a sprung bias in a proximal direction andis configured to be depressed into the dose dial grip 402 by a user ofthe device 100.

A spindle 414 is disposed centrally within the mechanism 400. Thespindle 414 is provisioned with at least one helical groove. In theembodiment depicted, the spindle 414 has two opposite handed overlappinggroove forms that preferably extend over at least a majority of a lengthof the spindle. Each groove form is effectively continuous over a numberof turns. In one preferred arrangement, each groove of the spindleengages either a non-continuous helical groove form on a body portion oron a driver. Preferably, either or both a non-continuous thread form ona body and a driver consists of less than one complete turn of thread. Afirst thread of the spindle 414 is configured to connect with a portionof the inner housing 408.

The dose setting mechanism 400 also comprises a spring 401, a clutch 405and a driver 409 having a first driver portion 407 and a second driverportion 412. These driver portions 407, 412 extend about the spindle414. Both the first and the second driver portions 407, 412 aregenerally cylindrical. The clutch 405 is disposed about the driver 409.In one arrangement, the first driver portion 407 comprises a firstcomponent part 410 and a second component part 411. Alternatively, thefirst driver portion 407 is an integral component part.

With the dose setting mechanism 400, as a user dials a dose with thedose dial grip 402, the metal spring 401 is selected to be strong enoughto maintain engagement of both clutched couplings: the clutched couplingbetween the clutch 405 and the encoded member 406 and clutched couplingbetween the first driver portion 407 and second driver portion 412. Theencoded member 406 is coupled to the dose dial grip 402 such that when auser rotates the dose dial grip 402, the encoded member 406 alsorotates. As the encoded member 406 is rotated in a first rotationaldirection, it moves axially in a proximal direction due to its threadedconnection to the inner housing 408.

When the drug delivery device is being dispensed, the user applies anaxial load to the dose delivery button 416 located at the proximal endof the mechanism 400. The dose delivery button dose delivery button 416is axially coupled to the clutch 405 and this prevents relative axialmovement. Therefore, the clutch 405 moves axially towards the cartridgeend or the distal end of the dose setting mechanism 400. This movementdisengages the clutch 405 from the encoded member 406, allowing forrelative rotation while closing up the Gap ‘a’. The clutch 405 isprevented from rotating relative to a clicker 420 and hence relative tothe inner housing 408. However, in this scenario, the coupling betweenthe first driver portion 407 and the second driver portion 412 is alsoprevented from becoming disengaged. Therefore, any axial load on thespindle 414 only disengages the first and second driver portions 407,412 when the dose delivery button dose delivery button 416 is notaxially loaded. This therefore does not happen during dispense.

A dose limiter 418 (visible in FIG. 4) is provided on first driverportion 407 and in the illustrated arrangement comprises a nut. The doselimiter 418 has an internal helical groove matching the helical grooveof the first driver portion 407. In one preferred arrangement, the outersurface of the dose limiter 418 and an internal surface of the innerhousing 408 are keyed together by way of splines. This prevents relativerotation between the dose limiter 418 and the housing 408 while allowingrelative longitudinal movement between these two components.

FIG. 6 shows in detail a first arrangement of the first driver portion407 and the second driver portion 412 illustrated in FIGS. 3 to 5. Asillustrated in FIG. 6, the second driver portion 412 is generallytubular in shape and comprises at least one drive dog 450 located at adistal end of the second driver portion 412. The first driver portion407 also has a generally tubular shape and comprises a plurality ofrecesses 452 sized to engage with the drive dog 450 on the second driverportion 412. The construction of the drive dog and recesses allowdisengagement with the drive dog 450 when the first and second driverportions are axially pushed together. This construction also creates arotational coupling when these components are sprung apart.

In some embodiments, the first driver portion 407 comprises a firstportion (first component part) 410 that is permanently clipped to asecond portion (second component part) 411. In this arrangement, thesecond component part 411 comprises the plurality of recesses 452 andthe first component part 410 includes the outer groove for the doselimiter 418 nut as well as an internal groove 454. This internal groove454 is used to connect to the spindle 414 and drives the spindle 414during dose administration. In the illustrated embodiment, the internalgroove 454 comprises a part helical groove rather than a completehelical groove. One advantage of this arrangement is that it isgenerally easier to manufacture.

One advantage of this dose setting mechanism 400 utilizing the innerhousing 408 is that the inner housing 408 can be made from anengineering plastic that minimizes friction relative to the encodedmember 406 groove guide 436 and the groove 432. For example, one suchengineering plastic could comprise Acetal. However, those skilled in theart will recognize that other comparable engineering plastics having alow coefficient of friction could also be used. Using such anengineering plastic enables the material for the outer housing 404 to bechosen for aesthetic or tactile reasons with no friction relatedrequirements since the outer housing 404 does not engage any movingcomponents during normal operation.

The effective driving diameter (represented by ‘D’) of the groovedinterface between the encoded member 406 and the inner housing 408 isreduced compared to certain known drug delivery devices for the sameouter body diameter. This improves efficiency and enables the drugdelivery device to function with a lower pitch (represented by ‘P’) forthis groove and groove guide connection. In other words, as the helixangle of the thread determines whether when pushed axially, the encodedmember will rotate or lock to the inner body wherein this helix angle isproportional to the ratio of P/D.

A recess 442 in the outer housing 404 of the drug delivery device 100can be seen in FIG. 3. This recess 442 may be configured to receive aninsert or electronic module (not shown), comprising the processor 202,ROM 204, flash memory 205, RAM 206, display electronics, contacts 212and batteries 214 previously described. Alternatively, the contacts 212may be supported at another position on the inner surface of the outerhousing 404 and linked to the processor 202 and batteries 214 byconductive paths or wires. The display mount 112 shown in FIG. 1 may bedisposed on top of the insert or may be integral with the insert. Thedisplay mount 112 is configured to support the display 210. The display210 may be larger than the recess 442 and may therefore protrude fromthe outer housing 404. Alternatively, both the display mount 112 anddisplay 210 may be configured to be received by the recess 442 such thatthe display 210 is flush with the outer surface of the outer housing404. The contacts 212 are configured to contact the encoded member 406in order to facilitate a determination of the rotational position of theencoded member 406, as will be described in more detail below.

The dose setting mechanism 400 illustrated in FIGS. 3-6 is configured tobe re-set to an initial position after the medicament in the attacheddrug cartridge has been expelled. This allows a new cartridge to beinserted and the drug delivery device 100 to be re-used. This re-settingmay be achieved by pushing axially on the distal end of the spindle 414i.e. the end which usually engages with the drug cartridge and does notrequire any mechanism associated with removal of a cartridge holder. Asillustrated in FIGS. 3 and 4, when the first driver portion 407 ispushed axially towards the second driver portion 412 (i.e., pushed in aproximal direction) the driver 409 is decoupled from the rest of thedose setting mechanism 400.

An axial force on the spindle 414 causes the spindle 414 to rotate dueto its threaded connection to the inner housing 408. This rotation andaxial movement of the spindle 414 in turn causes the first driverportion 407 to move axially towards the second driver portion 412. Thiswill eventually decouple the first driver portion 407 and second driverportion 412.

This axial movement of the first driver portion 407 towards the seconddriver portion 412 results in certain advantages. For example, oneadvantage is that the metal spring 401 will compress and will thereforeclose the Gap ‘a’ illustrated in FIGS. 3-5. This in turn prevents theclutch 405 from disengaging from the clicker 420 or from the encodedmember 406. The second driver portion 412 is prevented from rotationsince it is splined to the clutch 405. The clicker 420 is splined to theinner housing 408. Therefore, when the Gap ‘a’ is reduced or closed up,the second driver portion 412 cannot rotate relative to either the innerhousing 408 or the encoded member 406. As a consequence, the encodedmember 406 cannot rotate relative to the inner housing 404. If theencoded member 406 is prevented from rotating then, as the spindle 414is retracted back into the dose setting mechanism 400 and therebyre-set, there will be no risk of the encoded member 406 being pushed outof the proximal side of the dose setting mechanism 400 as a result of aforce being applied on the spindle 414.

Another advantage of a dose setting mechanism 400 comprising an innerhousing 408 is that the dose setting mechanism 400 can be designed, witha slight modification, as a drug delivery device platform that is nowcapable of supporting both re-settable and non-resettable drug deliverydevices. As just one example, to modify the re-settable dose settingmechanism 400 variant illustrated in FIGS. 3-6 into a non-resettabledrug delivery device, the first component part 410 and the secondcomponent part 411 of the first driver potion 407 and the second driverportion 412 can be moulded as one unitary part. This reduces the totalnumber of drug delivery device components by two. Otherwise, the drugdelivery device illustrated in FIGS. 3-6 could remain unchanged. In sucha disposable device, the second housing part 106 would be fixed to thefirst housing part 104 or alternatively made as a single one piece bodyand cartridge holder.

The dose setting mechanism described above is merely one example of amechanism suitable for supporting the encoded member 406 and forimplementing the present invention. It will be apparent to the skilledperson that other mechanisms may also be suitable. For example, amechanism which does not include an inner housing 408, but in which theencoded member 406 is still visible to the sensor 112 would be equallysuitable.

First Embodiment

In view of the foregoing it will be appreciated that a user twists therotatable dial 108 to select an amount of dose to be dispensed from adrug cartridge. This causes the encoded member 406 to rotate andtranslate axially (longitudinally) relative to the housing 102. Byanalysing information provided on the outer surface 440 of the encodedmember 406 the extent of rotation of the dial 108, and thus the amountof dose dialed, can be determined. Furthermore, a user presses the dosedelivery button 416 to dispense an amount of dose from within a drugcartridge. Pressing the dose delivery button 416 causes the encodedmember 406 to rotate and move axially the other way. Thus by analysinginformation provided on the outer surface 440 of the encoded member 406how far the encoded member 406 has been translated within the housing,and thus the amount of dose dispensed, can also be determined.

FIG. 7 illustrates an encoded member 406 according to a first embodimentof the present invention. The encoded member 406 is a hollow cylinder orsleeve having an outer surface 440 and an inner surface 438. The outersurface 440 comprises a helical track 300 forming an encoder. FIG. 7shows that the helical track comprises a series of conductive segments302 (shown in black) that are electrically coupled to one another by apower line 306 (also shown in black). Non-conductive or insulatingsegments 304 (shown in white) are defined in the space betweenrespective conductive segments 302.

A drug delivery device 100, according to a first embodiment thereof, isprovided with contacts 212 a-212 g that engage the helical track 300 atdifferent locations along the length of the track 300 as depicted inFIG. 8. It should be remembered that when the encoded member 406 iscaused to rotate, the encoded member 406 moves axially within thehousing 102. Since the contacts 212 a-212 g are fixed in positionrelative to the housing 102, rotating the encoded member 406 causesrespective conductive and non-conductive segments 302, 304 of thehelical track 300 to sweep across the contacts 212 a-212 g.

The processor 202 is capable of determining the extent of rotation ofthe encoded member 406 (and thus how far it has traveled axially) byanalysing which contacts 212 a-212 g engage conductive segments 302 andwhich contacts engage non-conductive segments 304. How this is achievedwill be explained in more detail below after the configuration of theencoded member 406 has been set out in more detail

Referring back to FIG. 7, the inner surface 438 of the encoded member406 may have a helical thread (shown as inner groove 436 in FIGS. 3 to5). This thread 436 may extend over a single turn or over a partialturn. Alternatively, this thread 436 may comprise several turns. Theencoded member 406 may be made of a plastic material. The encoded member406 is configured to be incorporated into the drug delivery device 100as shown in FIGS. 3 to 5. The inclusion of an inner housing 408 enablesthe encoded member 406 to have a helical thread 436 on the inner surface438 rather then the outer surface 440. This results in a number ofadvantages. For example, this results in the advantage of providing moresurface area along the outer surface 440 of the encoded member 406 forthe helical track 300. Another advantage is that this inner groove 436is now protected from dirt ingress. In other words, it is more difficultfor dirt to become lodged in this inner groove interface than if thegroove were provided along the outer surface 440 of the encoded member406. This feature is particularly important for a re-settable drugdelivery device which is required to function over a much longer periodof time compared to a non-resettable device.

The helical track 300 may be formed on the outer surface 440 of theencoded member 406 by wrapping a metallic strip around the encodedmember 406. Such a metallic strip may have a non-conductive backing tosupport the metallic layer. The non-conductive backing may have anadhesive on the reverse side for securing the strip to the outer surface440 of the encoded member 406. The helical track 300 may alternativelycomprise conductive ink printed onto a non-conductive substrate. Thisnon-conductive substrate may be the encoded member 406 itself or asecondary substrate which is subsequently attached to the encoded member406.

FIG. 9 illustrates the helical track 300 (which, as mentioned could be ametallic strip) in unwrapped form. Part of the track 300 in FIG. 9 isshown as being magnified. The conductive segments 302 (shown in black)are electrically coupled to one another via a power line 306 (also shownin black). It will therefore be appreciated that applying a voltage toone of the conductive segments 302 causes all of the conductive segments302 to be energised by virtue of their electrical connection to thepower line 306.

Preferably seven contacts 212 a-212 g are arranged around the encodedmember 406, as depicted in FIG. 8. The contacts 212 a-212 g are arrangedso as to engage the encoded member 406 at different locations along thelength of the helical track 300 (note that the seven contacts 212 a-212g do not engage the power line 306 and may only engage the conductiveand non-conductive segments 302, 304 of the helical track 300). Thecontacts 212 a-212 g may be angularly separated by 15 degrees relativeto one another along the length of the helical track 300. The pitch ofthe helix along which the contacts 212 a-212 g are formed is the same asthe pitch of the helix of the helical track 300, which is the same asthe pitch of the threads that constrain movement of the encoded member406 relative to the inner housing 408.

Displacing the contacts 212 a-212 g along the length of the helicaltrack 300 provides that, for a given rotational position of the encodedmember 406, some of the contacts 212 a-212 g engage conductive segments302 whereas the other contacts engage non-conductive segments 304. Thehelical track 300 shown in the drawings is configured such that for eachrotational position of the encoded member 406, at least two contacts 212a-212 g are in engagement with conductive segments 302.

Looking again at FIG. 8 the contacts 212 a-212 g are shown supported inthe recess 442 (the display mount 112 not being shown). The contacts 212a-212 g may be biased against the outer surface 440 of the encodedmember 406 in order to provide a stable electrical connection with thehelical track 300. Additionally, the contacts 212 a-212 g are inclinedrelative to the longitudinal axis of the device 100 by the same degreeas the pitch of the helical track 300. The pitch of the helical track300 is the same as the pitch of the groove guide 436 of the encodedmember 406 which engages with the inner housing groove 432. Therefore,when the encoded member 406 rotates and moves axially within the housing102, the helical track 300 is always positioned directly underneath thecontacts 212 a-212 g. More specifically the section of helical track 300comprising the conductive and non-conductive segments 302, 304 is alwayspositioned directly underneath the contacts 212 a-212 g. As previouslymentioned, the contacts 212 a-212 g do not engage the power line section306 of the helical track 300.

How the processor 202 is able to determine the extent of rotation of theencoded member 406 (and thus how far it moves axially) will now beexplained. The processor 202 is configured to address each of thecontacts 212 a-212 g individually. The processor 202 is also configuredto control the provision of a voltage signal from the batteries 214 toeach contact. However, when the batteries 214 provide a signal having avoltage to one of the contacts 212 a-212 g, certain others of thecontacts may also be energised by virtue of being in electricalconnection with the first contact via the power line 306. Thus, thebatteries may provide a voltage to a first of the contacts (for example,contact 212 a) and the processor 202 may detect signals from each of theother contacts that are energised due to being in electrical connectionwith the first contact 212 a through the power line 306. Since theprocessor 202 can address the contacts 212 a-212 g individually, it isable to apply a signal to different contacts, each time monitoringsignals from the other contacts.

It may be that the drug delivery device 100 shown in FIG. 1 is aninsulin pen type injection device. Users may need to set an insulin doseof between 1 and 80 International Units. Advantageously, the helicaltrack 300 utilised in conjunction with seven contacts 212 a-212 gprovides a seven bit encoding system. This allows 2⁷=128 discreterotational positions of the encoded member 406 to be uniquely encoded.Thus the full 0-80 unit dial-able dose for an injection device can beabsolutely encoded with redundant positions available.

The seven bit encoding system is realised by arranging the foregoingconductive and non-conductive segments 302, 304 of the helical track 300such that they form a type of code. FIG. 10 illustrates how the sevencontacts 212 a-212 g of the present embodiment (depicted as contacts1-7) move into and out of engagement with conductive and non-conductivesegments 302, 304 of the helical track 300 when the encoded member 406is moved rotationally (and thus axially) relative to the housing 102.

A code digit of “1” denotes that a contact engages a conductive segment302 whereas a code digit of “0” denotes that a contact engages anon-conductive segment 304. From FIG. 10 it will be apparent that whenthe seven contacts 212 a-212 g move along the helical track 300 (uponrotation and thus axial movement of the encoded member 406) the contactscome into engagement with various unique configurations of conductiveand non-conductive segments 302, 304. In particular, in the illustrativeexample of the present embodiment, the contacts encounter 81 uniqueconfigurations of conductive and non-conductive segments 302, 304 asthey move along the helical track 300.

FIG. 11 depicts a numerical representation of the track 300 in FIG. 9.From FIG. 11 the 81 unique seven bit binary codes associated with the 81unique rotational positions of the encoded member 406 can be determined.

When a user of the device 100 twists the rotatable dial 108 (see FIG. 8)to select or dial in a drug dose, the processor 202 may be activated andmay be controlled by software stored in the ROM 204 to execute a checkon the contacts 212 a-212 g to determine the absolute rotationalposition of the encoded member 406, and hence the drug dose which hasbeen dialed. The processor 202 may also be configured to determine thenumber of drug units which have been delivered.

The process of determining a dialed dose will now be described. In orderto determine the drug dose which has been dialed, the processor 202first causes the batteries 214 to apply a voltage to a first contact(for example, contact 212 a) and then the processor determines which ofthe remaining six contacts are energised. It should be remembered thatin the present embodiment, for each rotational position of the encodedmember 406 at least two contacts 212 a-212 g engage a conductive segment302 of the helical track 300. Thus when a voltage is applied to thefirst contact 212 a, if any of the remaining six contacts 212 b-212 gare energised then both the first contact and the other energisedcontacts are associated with a code value of “1”. This denotes that suchcontacts are in engagement with a conductive segment 302 of the track300. The contacts that were not energised are associated with a codevalue of “0”. This denotes that such contacts are in engagement with anon-conductive segment 302 of the track 300.

Analysing which contacts are associated with a code value of “1” andwhich are associated with a code value of “0”, the processor 202 candetermine the unique seven bit binary code associated with the absoluterotational position of the encoded member 406. The processor 202 canthen use the seven bit binary code to determine the dialed drug dose.This may be achieved by the processor 202 upon searching a lookup tablestored in the ROM 204, the lookup table providing a conversion from theseven bit binary code result to a dose unit dialed.

If however, when a voltage is applied to the first contact (for examplecontact 212 a) none of the other contacts 212 b-212 g are determined tobe energised then the processor 202 instead applies a voltage to anotherone of the contacts (for example, the second contact 212 b). Theprocessor then determines whether any of the other contacts areenergised upon applying a voltage to the second contact 212 b. Thisprocess is repeated for respective contacts until at least one of theseven contacts 212 a-212 g is detected as being energised uponapplication of a voltage to another one of those contacts. When this isdetected as taking place the processor 202 uses the seven bit binarycode associated with the absolute rotational position of the encodedmember 406 to determine the dialed dose in the manner heretoforedescribed. In particular the processor 202 compares the seven bit binarycode with a lookup table to determine the dialed dose amount.

As an illustrative example, before dialing a dose by twisting therotatable dial 108 the encoded member 406 may be in a positionassociated with the code depicted on the left-hand side in FIG. 10. Insuch a “0” position (i.e. the zero dose dialed position) the processor202 will detect the seventh contact 212 g to be energised when a voltageis applied to the first contact 212 a. This is because in position “0”only the first and seventh contacts 212 a, 212 g engage conductivesegments 302 of the helical track 300, whereas the other contacts 212b-212 f engage non-conductive segments 304. In effect the binary result“1000001” is read by the processor 202. From this the device 100 isdetermined by the processor 202 to be in the zero dose dialedconfiguration upon consulting a lookup table. This is because in such alookup table a dialed dose amount of “zero dose units” will beassociated with the binary code value “1000001”. It is envisaged that adialed dose amount of zero may be shown on the display 210 to a user ofthe drug delivery device 100.

Upon dialing a dose by twisting the rotatable dial 108 the encodedmember 406 may be moved into a position associated with the codedepicted on the right-hand side in FIG. 10 denoted as position “2”. Inthis configuration no additional contacts will be determined by theprocessor 202 to be energised when a voltage is applied to any ofcontacts one to four 212 a-212 d. However, upon applying a voltage tothe fifth contact 212 e the processor 202 will detect contact six 212 fas being energised. This is because in position “2” only the fifth andsixth contacts 212 e, 212 f engage conductive segments 302 of thehelical track 306. In effect the binary code “0000110” will be read bythe processor 202. From this the processor 202 can determine that Y doseunits have been dialed upon consulting the aforementioned lookup table.This is because in such a lookup table a dialed dose amount of Y doseunits will be associated with binary code value “0000110”. It isenvisaged that a dialed dose amount of Y dose units may be shown on thedisplay 210 to a user of the drug delivery device 100.

It will be appreciated that in other arrangements the code defined bythe helical track 300 may have a different configuration, in particularit may define a different combination of “0”s and “1”s to that used inthe above illustrative example.

In addition to (or instead of) determining a dialed dose, the device 100may be configured to determine an amount of dose that has beendispensed. For example, when an amount of dose has been dispensed theprocessor 202 may determine the position of the encoded member 406relative to the housing 102 in the foregoing manner. In particular theprocessor 202 may determine the seven bit binary code associated withthe absolute rotational position of the encoded member 406. The doseamount associated with such a binary code may then be determined from alookup table. The processor 202 may determine the drug dose which hasbeen dispensed (or is yet to be dispensed, if any) by subtracting aremaining drug dose from an initially dialed drug dose. It is envisagedthat the display 210 may be used to show the dose amount yet to bedispensed if a user does not dispense the full amount of a dialed dose.

Having determined the drug dose which has been dispensed, the processor202 may store the result in the flash memory 205. As mentioned above thedisplay 210 may be controlled to display the result of the dispenseddose determination. The display 210 may show the result of the dispenseddose determination for a predetermined time, for example 60 seconds.Alternatively or in addition, the dispensed dose history may beretrieved electronically from the flash memory 205 by a user of thedevice 100 or by a health care professional. During dialing of thedevice, the dialed dose may be indicated to the user in any conventionalway, for example by use of numerals printed on the encoded member. Insome other embodiments, the dialed dose is not determined or indicatedto the user.

Although a seven bit coding system has been described, the firstembodiment is equally applicable for any number of contacts greater thanthree, in other words at least contacts 212 a-212 d. The seven bitsystem is preferred as it allows the full 0-80 unit dose range to beabsolutely encoded.

Furthermore, the processor 202 may implement the process of checking thecontacts 212 a-212 g while the encoded member 406 is actually rotating,i.e. while the device 100 is actually being dialed or is being used todispense a substance. Alternatively the checking process may only beperformed when the processor 202 detects that the encoded member 406 hasbeen in a certain position for a predetermined amount of time (forexample 100 milliseconds), thereby indicating that the device 100 hasbeen dialed or dispensed an intended amount by a user.

Second Embodiment

FIG. 12 illustrates an encoded member 406 according to a secondenvisaged embodiment of the present invention. This encoded member 406differs from the embodiment shown in FIG. 7 in that the power line 306is slightly thicker, i.e. has a greater dimension in the axialdirection, in the present embodiment. In particular the power line 306depicted in FIG. 12 is thick enough to accommodate an additional, eighthelectrical contact 212 h.

FIG. 13 shows part of a drug delivery device 100 according to a secondembodiment thereof, the device 100 having an additional, eighth, contact212 h (the display mount 112 not being shown). The other sevenelectrical contacts 212 a-212 g are similar to those previouslydescribed in connection with FIG. 8 and, as in the previous embodiment,are configured to engage the conductive and non-conductive segments 302,304 of the helical track 300. In the present embodiment however thehelical track 300 and the contacts 212 a-212 g are arranged such that ineach rotational position of the encoded member 406 at least one (ratherthan at least two) of the seven contacts 212 a-212 g engage a conductivesegment 302 of the helical track 300.

The eighth contact 212 h is arranged to remain in contact with thethicker power line 306 when the encoded member 406 rotates and movesaxially relative to the housing (i.e. when a dose is being dialed ordispensed). As such, the eighth contact 212 h will be referred tohereafter as the power line contact 212 h.

In this embodiment of the drug delivery device 100 the processor 202 isconfigured to cause the batteries 214 to continually apply a voltage tothe power line contact 212 h when determining the absolute rotationalposition of the encoded member 406, and therefore an amount of dosedialed or dispensed. Furthermore, in the present embodiment the helicaltrack 300 and the contacts 212 a-212 g are arranged such that when avoltage is applied to the power line contact 212 h at least one of theseven contacts 212 a-212 g is energised.

Since the conductive segments 302 of the helical track 300 areelectrically coupled to one another via the power line 306, when avoltage is applied to the power line contact 212 h the other sevencontacts 212 a-212 g are energised whenever they engage a conductivesegment 302 of the helical track 300. This enables the processor 202 todetermine the absolute rotational position of the encoded member 406 ina different way to that previously described. In particular, thealgorithm of applying voltages to respective contacts 212 a-212 gone-by-one until at least one other contact is detected to be energisedis not necessary. Instead, applying a continuous voltage to the powerline 306 (via the power line contact 212 h) causes all contacts 212a-212 g in engagement with conductive segments 302 of the helical track300 to be energised. Therefore the processor 202 can determine theabsolute rotational position of the encoded member 406 by directlyanalysing which contacts 212 a-212 g are energised when the power linecontact 212 h is switched on.

For instance when a user of the drug delivery device 100 twists therotatable dial 108 to set a drug dose (see FIG. 13), the processor 202may be activated and controlled by software stored in the ROM 204 tocause the batteries 214 to apply a voltage to the power line contact 212h. The processor 202 may also be controlled by the software to execute acheck on the other seven contacts 212 a-212 g to determine which of themhave been energised. This enables the seven bit binary code associatedwith the absolute rotational position of the encoded member 406 to bedirectly determined by the processor 202. Comparing this binary codewith a lookup table in the manner heretofore described enables theamount of dose dialed to be determined.

Similarly an amount of dose that has been dispensed may be determined ina corresponding way. In particular when a dose amount has been dispensedthe processor 202 may directly determine which of the seven contacts 212a-212 g are energised upon causing the batteries 214 to apply a voltageto the power line contact 212 h. From this the seven bit binary codeassociated with the absolute rotational position of the encoded member406 may be assembled and compared with a lookup table in order todetermine a dose amount associated with that absolute rotationalposition. From this the processor 202 may then calculate the dose whichhas been dispensed (or is yet to be dispensed, if any) by subtracting aremaining dose amount from an initially dialed dose.

Further envisaged arrangements of the second embodiment described hereinwill now be briefly outlined.

Although a seven bit system has been described, the second embodiment isequally applicable for any number of position determining contactsgreater than three, in other words at least contacts 212 a-212 d shownin FIG. 13. This is of course in addition to the power line contact 212h. The seven bit system is advantageous as it allows the full 0-80 unitdose range to be absolutely encoded.

The processor 202 may implement the process of checking the contacts 212a-212 g, upon application of a voltage to the power line contact 212 h,while the encoded member 406 is actually rotating i.e. while the device100 is being dialed or is being used to dispense a dose. Alternativelythe checking process may only be performed when the processor 202detects that the encoded member 406 has been in a certain position for apredetermined amount of time (for example 100 milliseconds), therebyindicating that the device has been dialed or dispensed an intendedamount by a user.

Furthermore, the code defined by the helical track 300 may have adifferent configuration, in particular it may define a differentcombination of “0”s and “1”s to the code shown in FIG. 12. It isenvisaged that the conductive and non-conductive segments 302, 304 maybe arranged relative to the contacts 212 a-212 g to define a Gray codeor a reflected binary code.

Third Embodiment

FIGS. 14 a & 14 b illustrate front and reverse views of an encodedmember 406 according to a third embodiment of the present invention.This encoded member 406 differs from the embodiment shown in FIG. 7 inthat an additional track 308 is provided on the outer surface 440adjacent the helical track 300 which forms an encoder. As such, thehelical track 300 will be referred to hereafter as the first helicaltrack 300 and the additional track 308 will be referred to hereafter asthe second helical track 308.

FIG. 15 shows these two tracks in unwrapped form and it will beappreciated that the second helical 308 track essentially comprises acontinuous electrically conductive member. The pitch of the secondhelical track 308 is the same as the pitch of the first helical track300. Also, the distance between the two helical tracks and the sectionslabelled a) and b) in FIG. 15 may be varied, for example they may begreater or smaller provided that the separate helical tracks 300, 308 donot electrically connect with one another. In one particular arrangementthe sections labelled a) and b) in FIG. 15 may be set at half thecircumference of the encoded member's outer surface 440.

A drug delivery device 100, according to a third embodiment thereof, isprovided with an additional, eighth, contact 212 i. FIG. 16 (in whichthe display mount 112 is not shown) depicts such an additional contact212 i, wherein contacts 212 a-212 g are the same as those illustrated inFIG. 8. As such, the seven contacts 212 a-212 g engage conductive andnon-conductive segments 302, 304 of the first helical track 300 duringrotation of the encoded member 406. The additional, eighth, contact 212i is arranged to remain in contact with the second helical track 308when the encoded member 406 rotates and moves axially relative to thehousing (i.e. when a dose is being dialed or dispensed). For reasonswhich will become apparent later the eighth contact 212 i will bereferred to hereafter as the mode-shift contact 212 i.

An electrical conduction path (not shown) may join the first and secondhelical tracks 300, 308. The switch 216 (see FIG. 2) is disposed in thiselectrical conduction path. The switch 216 is configured to connectelectrically the first and second helical tracks 300, 308 when thedevice 100 is idle or when a drug dose is being set by rotation of therotatable dial 108 (see FIG. 16). This allows the processor 202 todetermine that the device 100 is in dialing mode. The switch 216 is alsoconfigured to isolate electrically, or disconnect, the first and secondhelical tracks 300, 308 when a drug dose is being delivered. This allowsthe processor 202 to determine that the device 100 is in dispensingmode.

In particular the switch 216 may be coupled to the dose delivery button416 (see FIG. 3) supported by the rotatable dial 108, such that when thebutton is depressed, the switch 216 disconnects the first and secondhelical tracks 300, 308.

When a drug delivery device 100 according to the present embodiment isin use the processor 202 determines the absolute rotational position ofthe encoded member 406 in the manner heretofore described in connectionwith the first embodiment shown in FIG. 7. In particular the processor202 is activated and controlled by software stored in the ROM 204 toexecute a check on the contacts 212 a-212 g shown in FIG. 16 todetermine the seven bit binary code associated with the absoluterotational position of the encoded member 406. In the present embodimenthowever the processor 202 is additionally configured to determine thestatus of the switch 216 and hence whether the device 100 is in dialingor dispensing mode.

The process of determining a dialed dose will now be described. When auser twists the rotatable dial 108 (see FIG. 16) in order to dial adose, the switch 216 electrically couples the first and second helicaltracks 300, 308 to one another (if they were not previously coupled).The processor 202 then determines the absolute rotational position ofthe encoded member 406 by causing a voltage to be applied to a firstcontact (for example, contact 212 a) and then analysing which of theremaining six contacts are energised. It should be remembered that foreach rotational position of the encoded member 406 at least two contacts212 a-212 g engage a conductive segment 302 of the first helical track300. Thus when a voltage is applied to the first contact 212 a if any ofthe remaining six contacts 212 b-212 g are energised then both the firstcontact and the other energised contacts are associated with a codevalue of “1”. The contacts that are not energised are associated with acode value of “0”.

Due to the electrical connection between the first and second helicaltracks 300, 308 if the first contact 212 a is associated with a codevalue of “1” then the mode-shift contact 212 i will also be energisedwhen a voltage is applied to the first contact 212 a. This enables theprocessor 202 to determine that the drug delivery device 100 is indialing mode. Using the measured code values to determine the seven bitcode associated with the rotational position of the encoded member 406,the processor 202 can thus determine the dialed dose for example byconsulting a lookup table stored in the ROM 204.

However, if when a voltage is applied to the first contact (for examplecontact 212 a) none of the other seven contacts 212 b-212 g areenergised then the processor 202 instead applies a voltage to anotherone of the contacts (for example, the second contact 212 b in FIG. 16).The processor then determines whether any of the other contacts 212 aand 212 c-212 g are energised upon applying a voltage to the secondcontact 212 b. This process is repeated for respective contacts, namelycontacts 212 a-212 g, until at least one of the seven contacts 212 a-212g is detected as being energised upon application of a voltage toanother one of those contacts. When this is detected, since in thedialing mode the switch 216 electrically couples the first and secondhelical tracks 300, 308 then the mode-shift contact 212 i will also beenergised. Detecting this enables the processor 202 to determine thatthe drug delivery device 100 is in dose dialing mode. Furthermore, theprocessor 202 uses the seven bit code associated with the absoluterotational position of the encoded member 406 to determine the dialeddose in the foregoing manner.

Operation of the device 100 in dialing mode will now be brieflysummarized. When a voltage is applied to one of the seven contacts 212a-212 g, if any other contact and the mode-shift contact 212 i areenergised then the processor 202 can determine i) the seven bit codeassociated with the rotational position of the encoded member 406 andii) knowledge that the device is in dialing mode. This informationenables the processor 202 to determine the dialed dose for example bysearching a lookup table stored in the ROM 204, the lookup tableproviding a conversion from the seven bit binary code result to a doseunit dialed. Also it is envisaged that the processor 202 may beconfigured to control the display 210 to show specific symbol(s) or textto indicate to a user of the device 100 that the device is in dialingmode.

In addition to (or instead of) determining a dialed dose, a drugdelivery device 100 of the present embodiment may be configured todetermine an amount of dose that has been dispensed. For example, whenthe dose delivery button 416 is pressed the switch 216 may electricallydecouple the first and second helical tracks 300, 308. When an amount ofdose has been dispensed the processor 202 may determine the position ofthe encoded member 406 relative to the housing 102 (i.e. by determiningthe seven bit binary code associated with the rotational position of theencoded member 406). Since the first and second helical tracks 300, 308are electrically isolated when a dose is being dispensed, applying avoltage to any of the seven contacts 212 a-212 g to determine theaforementioned seven bit code will not cause the mode-shift contact 212i to become energised. This enables the processor to determine that thedrug delivery device 100 is in dispensing mode. It is envisaged that theprocessor 202 may be configured to control the display 210 to showspecific symbol(s) or text to indicate to a user of the device 100 thatthe device is in dispensing mode.

In other words when the seven bit code associated with a rotationalposition of the encoded member 406 is being determined, if themode-shift contact 212 i is not detected as being energised then thedrug delivery device 100 is determined by the processor 202 to be indispensing mode. The dose amount associated with such a binary code maybe determined from a lookup table and compared with the dialed dose(i.e. the dose originally intended to be dispensed). The processor 202may determine the dose which has been dispensed (or is yet to bedispensed, if any) by subtracting a remaining dose amount from theinitially dialed dose. The display 210 may be used to show the doseamount yet to be dispensed if for any reason a user does not dispensethe full amount of a dialed dose.

Having determined the drug dose which has been dispensed, the processor202 may store the result in the flash memory 205. As mentioned above thedisplay 210 may be controlled to display the result of the dispenseddose determination. The display 210 may display the result of thedispensed dose determination for a predetermined time, for example 60seconds. Alternatively or in addition, the dispensed dose history may beretrieved electronically from the flash memory 205 by a user of thedevice 100 or by a health care professional. During dialing of thedevice 100 the dialed dose may be indicated to the user in anyconventional way, for example by use of numerals printed on the encodedmember 406. In some other embodiments, the dialed dose is not determinedor indicated to the user.

One envisaged configuration of the switch 216 for electrically couplingand decoupling the first and second helical tracks 300, 308 will now bedescribed with reference to FIGS. 17 a to 17 c. Such a switch 216comprises part of a dose delivery button 416 and part of an encodedmember 406. More specifically the aforementioned clutch is locked to thedose delivery button 416 comprising part of the switch 216, and therotatable dial 108 is provided by a grip (such as a series of protrudingparts) located on the outer surface of the button 416. Furthermore, aconductive ring 256 is positioned in a cavity defined by the dosedelivery button 416 within which the encoded member 406 (FIG. 17 a) isalso received.

The encoded member 406 which comprises part of above mentioned switch216 has two resiliently deformable arms 258. Part of the first helicaltrack 300 is located on one deformable arm, and part of the secondhelical track 308 is located on the other deformable arm. When the dosedelivery button 416 is not pressed by a user (for example in dialingmode), the conductive ring 256 is positioned in physical contact withthe sections of track located on the deformable arms 258. In effect thiscloses the switch and the first and second helical tracks 300, 308 areelectrically coupled. When the dose delivery button 416 is pressedhowever (for example in dispensing mode), the button 416 shifts relativeto the encoded member 406 a distance such that the conductive ring 256is brought out of physical contact with the sections of track on theresiliently deformable arms 258. In effect this closes the switch andthe first and second helical tracks 300, 308 are electricallyde-coupled.

Further envisaged arrangements of the third embodiment described hereinwill now be briefly outlined.

Although a seven bit system has been described, the third embodiment isequally applicable for any number of position determining contactsgreater than three, in other words at least contacts 212 a-212 d shownin FIG. 16. This is of course in addition to the mode-shift contact 212i. The seven bit system is preferred as it allows the full 0-80 unitdose range to be absolutely encoded.

The processor 202 may perform the process of checking the contacts 212a-212 g and 212 i while the encoded member 406 is actually rotating,i.e. while the device 100 is being dialed or is being used to dispense asubstance. Alternatively the checking process may only be performed whenthe processor 202 detects that the encoded member 406 has been in acertain position for a predetermined amount of time (for example 100milliseconds), thereby indicating that the device 100 has been dialed ordispensed an intended amount by a user.

Configuration of the switch 216 may also be reversed. For instance theswitch 216 may be configured to electrically decouple the first andsecond helical tracks 300, 308 when the device 100 is idle or when adrug dose is being set by rotation of the rotatable dial 108. Such aswitch 216 is configured to electrically couple the first and secondhelical tracks 300, 308 when the selected drug dose is being delivered.The switch 216 may be coupled to the dose delivery button 416 supportedby the rotatable dial 108, such that when the button is depressed, theswitch 216 connects the first and second helical tracks 300, 308.

Furthermore, the code defined by the first helical track 300 may have adifferent configuration, in particular it may define a differentcombination of “0”s and “1”s to the track shown in FIGS. 14 and 15.

Fourth Embodiment

FIGS. 18 a & 18 b illustrate front and reverse views of an encodedmember 406 according to a fourth embodiment of the present invention.This encoded member 406 is similar to the embodiment shown in anddescribed with reference to FIG. 12 in that it is also provided with ahelical track 300 which forms an encoder, the track 300 having arelatively thicker power line 306. However in the present embodiment theencoded member 406 is also provided with an additional helical track 308similar to the one illustrated in FIGS. 14 a and 14 b.

The additional track 308 shown in FIGS. 18 a and 18 b is configured tobe engaged by an additional, ninth, contact, namely, a mode-shiftcontact 212 i. This enables the processor 202 to determine whether adrug delivery device 100, according to a fourth embodiment thereof, isin dialing mode or dispensing mode.

As before when describing the third embodiment of the present invention,the helical track 300 shown in FIG. 18 will be referred to hereafter asthe first helical track 300 and the additional track 308 will bereferred to hereafter as the second helical track 308. It will beappreciated that the second helical track 308 essentially comprises acontinuous electrically conductive member having the same pitch as thefirst helical track 300.

In order for the processor 202 of the present embodiment to determinewhether the drug delivery device 100 is in dialing mode or dispensingmode, the device 100 is provided with the mode-shift contact 212 i.Thus, in total, a drug delivery device 100 according to a fourthembodiment thereof is provided with nine contacts 212 a-212 i. Forinstance the seven contacts 212 a-212 g used to engage the conductiveand non-conductive segments 302, 304 of the first helical track 300during rotation of the encoded member 406. A power line contact 212 hfor engaging the power line 306 of the first helical track 300 duringrotation of the encoded member 406. A mode-shift contact 212 i forengaging the second helical track 308 during rotation of the encodedmember 406.

An electrical conduction path (not shown) may join the first and secondhelical tracks 300, 308. The switch 216 (see FIG. 2) is disposed in thiselectrical conduction path. The switch 216 may be configured to connectelectrically the first and second helical tracks 300, 308 when thedevice 100 is idle or when a drug dose is being set by rotation of therotatable dial 108. The switch 216 may be configured to isolateelectrically, or disconnect, the first and second helical tracks 300,308 when the selected drug dose is being delivered. In particular theswitch 216 may be coupled to the dose delivery button 416 supported bythe rotatable dial 108 such that when the button is depressed the switch216 disconnects the first and second helical tracks.

When a drug delivery device 100 according to the present embodiment isin use the processor 202 may determine the absolute rotational positionof the encoded member 406 in the same manner heretofore described inconnection with the second embodiment shown in FIG. 12. As in the secondembodiment, the first helical track 300 and the contacts 212 a-212 g arearranged such that when a voltage is applied to the power line contact212 h at least one of the seven contacts 212 a-212 g is energised.

The processor 202 may be activated and controlled by software stored inthe ROM 204 to cause the batteries 214 to apply a voltage to the firsthelical track 300 through the power line contact 212 h. The processormay also execute a check on the seven contacts 212 a-212 g to determinethe seven bit binary code associated with the absolute rotationalposition of the encoded member 406. Furthermore, in the presentembodiment the processor 202 is additionally configured to determine thestatus of the switch 216 and hence whether the device 100 is in “dialingmode” or “dispensing mode”.

The process of determining a dialed dose will now be described. When auser twists the rotatable dial 108 in order to dial a dose, the switch216 electrically couples the first and second helical tracks 300, 308shown in FIGS. 18 a and 18 b to one another (if they were not coupledpreviously). The processor 202 then determines the absolute rotationalposition of the encoded member by causing a voltage to be applied to thepower line contact 212 h and then analysing which of the seven contacts212 a-212 g are energised. It should be remembered that for eachrotational position of the encoded member 406 at least one contact 212a-212 g engages a conductive segment 302 of the first helical track 300.Thus when a voltage is applied to the power line contact 212 h at leastone contact 212 a-212 g should be energised. Any energised contacts areassociated with a code value of “1”. The contacts that are not energisedare associated with a code value of “0”. Due to the electricalconnection between the first and second helical tracks 300, 308 applyinga voltage to the first helical track 300 via the power line contact 212h will also cause the second helical track 308, and thus the mode-shiftcontact 212 i, to be energised. This enables the processor 202 todetermine that the drug delivery device 100 is in dialing mode. Usingthe foregoing code values to determine the seven bit code associatedwith the rotational position of the encoded member 406, the processor202 can thus determine a dialed dose amount.

Operation of the device 100 in dialing mode will now be brieflysummarized. In particular, in dialing mode when a voltage is applied tothe power line contact 212 h at least one of the seven contacts 212a-212 g in addition to the mode-shift contact 212 i will be energised.By analysing which contacts are energised at a particular point in timethe processor 202 can determine i) the seven bit code associated withthe absolute rotational position of the encoded member 406 and ii)knowledge that the device 100 is in dialing mode. This informationenables the processor 202 to determine the dialed dose for example bysearching a lookup table stored in the ROM 204, the lookup tableproviding a conversion from the seven bit binary code result to a doseunit dialed. It is also envisaged that the processor 202 may beconfigured to control the display 210 to show specific symbol(s) or textto indicate to a user of the device 100 that the device is in dialingmode.

In addition to (or instead of) determining a dialed dose, the drugdelivery device 100 of the present embodiment may be configured todetermine an amount of dose that has been dispensed. For example, whenthe dose delivery button 416 is pressed the switch 216 may electricallydecouple the first and second helical tracks 300, 308. When an amount ofdose has been dispensed the processor 202 may determine the position ofthe encoded member 406 relative to the housing 102 (i.e. by applying avoltage to the power line contact 212 h and using contacts 212 a-212 gto determine the seven bit binary code associated with the rotationalposition of the encoded member 406). Since the first and second helicaltracks 300, 308 are electrically isolated when a dose is beingdispensed, applying a voltage to the power line contact 212 h will notcause the mode-shift contact 212 i to be energised. Detecting this astaking place enables the processor 202 to determine that the drugdelivery device 100 is in dispensing mode. It is envisaged that theprocessor 202 may be configured to control the display 210 to showspecific symbol(s) or text to indicate to a user of the device 100 thatthe device is in dispensing mode.

Operation of the device 100 in dispensing mode will now be brieflysummarized. When the seven bit code associated with a rotationalposition of the encoded member 406 is determined, if the mode-shiftcontact 212 i is not detected as being energised then the drug deliverydevice 100 is determined by the processor 202 to be in dispensing mode.The dose amount associated with such a binary code may be determinedfrom a lookup table and compared with the dialed dose (i.e. the doseoriginally intended to be dispensed). The processor 202 may determinethe dose which has been dispensed (or is yet to be dispensed, if any) bysubtracting a remaining dose amount from the initially dialed dose. Thedisplay 210 may be used to show the dose amount yet to be dispensed iffor any reason a user does not dispense the full amount of a dialeddose.

Having determined the drug dose which has been dispensed, the processor202 may store the result in the flash memory 205. As mentioned above thedisplay 210 may be controlled to display the result of the dispenseddose determination. The display 210 may display the result of thedispensed dose determination for a predetermined time, for example 60seconds. Alternatively or in addition, the dispensed dose history may beretrieved electronically from the flash memory 205 by a user of thedevice 100 or by a health care professional. During dialing of thedevice, the dialed dose may be indicated to the user in any conventionalway, for example by use of numerals printed on the encoded member. Insome other embodiments, the dialed dose is not determined or indicatedto the user.

It is envisaged that the switch 216 may have the same configuration asthat previously described in connection with FIGS. 17 a to 17 c.

Further envisaged arrangements of the fourth embodiment described hereinwill now be briefly outlined.

Although a seven bit system has been described, the fourth embodiment isequally applicable for any number of position determining contactsgreater than three, in other words at least contacts 212 a-212 d. Thisis of course in addition to the power line contact 212 h and themode-shift contact 212 i. The seven bit system is preferred as it allowsthe full 0-80 unit dose range to be absolutely encoded.

The operation of the switch 216 may be reversed. In this alternativearrangement the switch 216 is configured to electrically decouple thefirst and second helical tracks 300, 308 when the device 100 is idle orwhen a drug dose is being set by rotation of the rotatable dial 108. Theswitch 216 is configured to electrically couple the first and secondhelical tracks 300, 308 when the selected drug dose is being delivered.The switch 216 may be coupled to the dose delivery button 416 supportedby the rotatable dial 108 such that when the button is depressed theswitch 216 connects the first and second helical tracks 300, 308.

The processor 202 may perform the process of checking the contacts 212a-212 g and 212 i, upon application of a voltage to the power linecontact 212 h, while the encoded member 406 is actually rotating i.e.while the device is being dialed or is being used to dispense asubstance. Alternatively the checking process may only be performed whenthe processor 202 detects that the encoded member 406 has been in acertain position for a predetermined amount of time (for example 100milliseconds), thereby indicating that the device has been dialed ordispensed an intended amount by a user.

Furthermore, the code defined by the first helical track 300 may have adifferent configuration, in particular it may define a differentcombination of “0”s and “1”s to the track 300 shown in FIGS. 18 a and 18b. It is envisaged that the conductive and non-conductive segments 302,304 may be arranged relative to the contacts 212 a-212 g to define aGray code or a reflected binary code.

Fifth Embodiment

It will be appreciated that in the foregoing embodiments the seven bitencoding system defined by i) the helical track 300 and ii) the sevencontacts 212 a-212 g, is what enables the absolute rotational positionof the encoded member 406 to be determined (which thereby enables thedialed/dispensed dose amount to be determined). In light of this it isfurther envisaged that the seven bit encoding system need notnecessarily be limited exclusively to electrically conductive membersonly.

In a fifth embodiment of the present invention the seven bit codingsystem could alternatively comprise i) a series of markings (such asprinted dots) forming an encoder on the outer surface 440 of an encodedmember 406, such markings defining a code and ii) seven optical sensors.An unwrapped view of a track which defines such an optically readablecode is illustrated in FIG. 19. The optically readable code defined bythe track in FIG. 19 corresponds to the code defined by the helicaltrack 300 shown in FIG. 9. More specifically, the optically readablecode may be located on an encoded member 406 such that the markings(i.e. the printed dots for example) are located in similar positions tothe conductive segments 302 in FIG. 7.

In such an arrangement the seven optical sensors may be positionedrelative to the encoded member 406 in similar positions to the contacts212 a-212 g in FIG. 8. For instance the optical sensors may beconfigured to analyse corresponding parts of the encoded member's outersurface 440 which the contacts 212 a-212 g otherwise engage in theembodiments previously described herein. The optical sensors may takeany suitable form. The optical sensors are configured to provide anoutput signal that is different when a marking is present in the area ofthe optically readable code to an output signal that is provided when amarking is not present in the area of the optically readable code. Inthis way, the sensor output indicates whether or not a marker is presentat the relevant location on the optically readable code. The opticalsensors may be active (for instance including an illuminating lightsource) or they may be passive (relying on ambient light to detect thecode).

An example of a suitable optical sensor arrangement comprises sevenindividual optical reflective type sensors arranged in a row. Since suchsensors are of the reflective type they are used to analyse theintensity of light reflected from the encoded member's outer surface440. It will be appreciated that the intensity of such reflected lightchanges depending on whether or not a marking is present in an area ofoptically readable code.

In a fifth embodiment of the drug delivery device 100, the processor 202is configured to continually observe outputs of the optical sensors whendetermining the absolute rotational position of the encoded member 406and thus the dose dialed or dispensed.

For instance by continually observing outputs of the optical sensors theprocessor 202 can determine the absolute rotational position of theencoded member 406 by directly analysing which optical sensors aredirected towards a marking on the encoded member's outer surface 440.Such markings correspond with the conductive segments 302 previouslydescribed and the spaces between the optically readable markingscorrespond with the non-conductive segments 304 previously described.

When a user of a drug delivery device 100, according to a fifthembodiment thereof, rotates the rotatable dial 108 to set or dial in adrug dose, the processor 202 may be activated and may be controlled bysoftware stored in the ROM 204 to apply a voltage to the opticalsensors. The processor 202 may also be controlled by the software toexecute a check on the optical sensors to determine which of them aredirected towards a code marking (a printed dot for example) on theencoded member 406. This enables the seven bit binary code associatedwith the absolute rotational position of the encoded member 406 to bedirectly determined by the processor 202. In the present embodiment theoptical sensors are may be arranged such that in each rotationalposition of the encoded member 406 at least one optical sensor isdirected towards a code marking. In particular, those sensors detectedas being directed towards a code marking are associated with a codevalue of “1”. The sensors directed towards a space between code markingsare associated with a code value of “0”. Comparing this binary code witha lookup table in the manner heretofore described enables an amount ofdose dialed to be determined. Similarly an amount of dose that has beendispensed (or is yet to be dispensed, if any) may be determined in acorresponding manner.

Additional envisaged arrangements of the fifth embodiment describedherein will now be briefly outlined.

Although a seven bit system has been described, the fifth embodiment isequally applicable for any number of optical sensors greater than three.The seven bit system is preferred as it allows the full 0-80 unit doserange to be absolutely encoded.

The processor 202 may perform the process of checking the opticalsensors while the encoded member 406 is actually rotating i.e. while thedevice 100 is being dialed or is being used to dispense a substance.Alternatively the checking process may only be performed when theprocessor 202 detects that the encoded member 406 has been in a certainposition for a predetermined amount of time (for example 100milliseconds), thereby indicating that the device has been dialed ordispensed an intended amount by a user.

The optically readable code (such as the one in FIG. 19) may be locatedwithin the tick marks of a number scale presented on the encoded member406 as shown in FIG. 22. Here the filled (black) circles represent “1”code values and the unfilled (white) circles represent “0” code values.

Furthermore, the code defined by the optically readable helical trackmay have a different configuration, in particular it may define adifferent combination of “0”s and “1”s to the track shown in FIG. 19. Itis envisaged that the optically readable helical track may be arrangedrelative to the optical sensors to define a Gray code or a reflectedbinary code.

Sixth Embodiment

With reference to FIG. 20, a sixth embodiment of the drug deliverydevice 100 differs from the previously described fifth embodiment inthat the device also has a mode-shift sleeve 444 located around at leastpart of the encoded member 406.

At least one of the optical sensors in the sixth embodiment should (asin the fifth embodiment) be capable of detecting optically readable codeon the encoded member's outer surface 440. Such sensors will be referredto hereafter as code-detecting sensors.

Additionally however the drug delivery device 100, according to a sixthembodiment thereof, is capable of processing image data acquired by atleast one optical sensor to determine the position of opaque lines 446(or similar markings, for instance dashed or dotted lines) on themode-shift sleeve 444. Optical sensors used for this purpose will bereferred to hereafter as imaging devices and may comprise a camera forexample. In particular, one or more imaging devices may be provided thatprocess image data to determine the position of opaque lines 446.Alternatively however, the processor 202 may be used to process imagedata acquired by the or each imaging device in order to determine theposition of opaque lines 446.

A suitable combination of optical sensors for the purposes of the sixthembodiment includes seven code-detecting sensors, such as the opticalsensors heretofore described in connection with the fifth embodiment(i.e. seven individual optical reflective type sensors arranged in arow). In addition to these sensors however an imaging device is alsoprovided that can be used to determine the position of opaque lines 446on the mode-shift sleeve 444.

Looking at FIG. 20, a mode-shift sleeve 444 is sufficiently transparentfor code-detecting sensors to detect the presence of code-definingmarkings located on the encoded member 406 therethrough. As alreadymentioned, a series of opaque lines 446 are provided on the mode-shiftsleeve. The distance between such lines is no less than the width of amarking associated with a code value provided on the encoded member 406(see FIG. 21). The sleeve 444 is arranged to rotate when a dose isdialed, but not to rotate when a dose is being dispensed. This may beachieved by coupling the mode-shift sleeve 444 to the dose deliverybutton 416. Thus when a user twists the dial 108 to set or dial in adose, the sleeve 444 rotates with the dial 108. However, when a userpresses the dose delivery button 416, since the button is configured tomove only axially (without rotating) when a dose is being dispensed themode-shift sleeve 444 moves axially also.

The movement of the opaque lines 446 across the field of view of theimaging device(s) can be used to determine the mode of operation of thedrug delivery device 100. In view of the foregoing it will beappreciated that when a user twists the dial 108 to set or dial in adose, the encoded member 406 is caused to rotate and the opaque lines446 are caused to sweep across the field of view of the imagingdevice(s). Detecting the occurrence of such lines 446 sweeping acrossthe field of view of the imaging device(s) enables the processor 202 todetermine that the drug delivery device 100 is in dialing mode. Thus,analysing the code located on the encoded member 406 using thecode-detecting sensor(s) allows the processor 202 to determine an amountof dose that has been dialed.

When a dose is being dispensed the opaque lines 446 are not caused tosweep across the field of view of the imaging device(s), however theencoded member 406 is caused to rotate in the manner heretoforedescribed. Detecting the occurrence of only markings on the encodedmember 406 sweeping across the field of view of the imaging device(s),and not the opaque lines 446, enables the processor 202 to determinethat the drug delivery device 100 is in dispensing mode. Thus, analysingthe code on the encoded member 406 using the code-detecting sensor(s)allows the processor 202 to determine an amount of dose that has beendispensed (or is yet to be dispensed, if any).

The mode-shift sleeve 444 may be configured and arranged such that ineach position of the encoded member that is associated with a unit ofdose (0, 1, 2 . . . 80 International Units for example), the opaquelines 446 extend around markings which define the optically readablecode as in FIG. 21. Furthermore, in each position of the encoded memberthat is associated with a unit of dose each opaque line 446 may belocated in the field of view of at least one imaging device.

In embodiments that use conductive track, sensing of the presence orabsence of track is performed using a contact and the processor. At ageneral level, this may involve hardware that compares a voltage signalprovided by the contact with a threshold and indicting the presence orabsence of track through an output that indicates whether the voltageexceeded or did not exceed respectively the threshold. In a processorimplementation, it may involve buffering the signal provided by thecontact, for instance using an inverter gate or other buffer, samplingthe buffered signal and comparing the sampled signal to a reference.Other ways of sensing the presence or absence of track will be apparentto the skilled person.

Finally, it will be appreciated that the above described embodiments arepurely illustrative and are not limiting on the scope of the invention.Other variations and modifications will be apparent to persons skilledin the art upon reading the present application. Moreover, thedisclosure of the present application should be understood to includeany novel features or any novel combination of features eitherexplicitly or implicitly disclosed herein or any generalization thereofand during the prosecution of the present application or of anyapplication derived therefrom, new claims may be formulated to cover anysuch features and/or combination of such features.

1-14. (canceled)
 15. A drug delivery device comprising: a housing; acylindrical member rotatably supported within the housing; and aplurality of sensors; wherein: the outer surface of the cylindricalmember is provided with a single track, the track forming an encoder andhaving a plurality of first track segments and a plurality of secondtrack segments arranged along the length of the track which arerespectively capable of inducing first and second responses in thesensors; and in each rotational position of the cylindrical memberrelative to the housing at least one different first track segment iscapable of inducing a first response in at least one said sensor,thereby enabling the rotational position of the cylindrical memberrelative to the housing to be determined.
 16. The device of claim 15,further comprising a processor configured to determine the rotationalposition of the cylindrical member relative to the housing by analysingsignals output from each of the sensors which correspond with whether afirst said response or a second said response is induced in a respectivesaid sensor.
 17. The device of claim 16, wherein the sensors eachcomprise an electrical contact, and the first and second track segmentsrespectively have lower and higher values of electrical resistance, thefirst track segments being electrically coupled to one another.
 18. Thedevice of claim 17, wherein the processor is configured to cause anelectrical signal to be applied to one of the electrical contacts whilesimultaneously detecting whether any of the other electrical contactsare energised, thereby enabling the rotational position of thecylindrical member relative to the housing to be determined.
 19. Thedevice of claim 17, wherein the processor is configured to cause anelectrical signal to be applied to each of the first track segments viaan additional electrical contact while simultaneously detecting whetherany of the other electrical contacts are energised, thereby enabling therotational position of the cylindrical member relative to the housing tobe determined.
 20. The device of claim 19, wherein the additionalelectrical contact engages a section of the track which electricallycouples the first track segments to one another.
 21. The device of claim17, further comprising an additional track located adjacent the trackforming said encoder, said additional track being electricallyconductive and in engagement with a further electrical contact, whereinthe processor is configured to analyse signals from the furtherelectrical contact to determine the operational mode of said device. 22.The device of claim 21, further comprising a switch configured toelectrically couple the two tracks in one operational mode of saiddevice, and to electrically decouple the two tracks in anotheroperational mode of said device.
 23. The device of claim 22, furthercomprising a delivery button configured to cause expulsion of a drugfrom the drug delivery device upon actuation thereof by a user, whereindepression of the delivery button changes a state of the switch.
 24. Thedevice of claim 15, wherein the sensors each comprise an optical sensor,and the first and second track segments respectively comprisedifferently coloured parts of said track.
 25. The device of claim 22,wherein the processor is configured to determine which of said opticalsensors are directed towards a first track segment and which of saidoptical sensors are directed towards a second track segment, therebyenabling the rotational position of the cylindrical member relative tothe housing to be determined.
 26. The device of claim 24, furthercomprising a sleeve which surrounds at least part of said cylindricalmember and which rotates relative to the optical sensors in oneoperational mode of the device but not in another operational mode ofthe device, and an additional optical sensor for use in monitoring therotational position of opaque markings provided on the sleeve in orderto determine the mode of operation of the device.
 27. The device ofclaim 16, wherein the processor is configured to determine a selecteddrug dose by searching a lookup table stored in a memory, the lookuptable providing a conversion between a rotational position of thecylindrical member relative to the housing and a selected drug dose. 28.The device of claim 27, wherein the processor is configured to determinea delivered drug dose by subtracting a remaining drug dose from theselected drug dose.